That didn't seem to make any difference, still prints to 24 pages.
A:H prints Page 1 (although could be to Col I, as I don't have grid lines shown and Col I is blank)
I:R prints Page 2 (which is 10 columns)

Code as below

Sub Print_Per()
Dim i As Integer
Application.ScreenUpdating = False
With Sheets("Month")
With .PageSetup
.PrintArea = "$A$66:$GU$99"
.Orientation = xlLandscape
.Draft = False
.PaperSize = xlPaperA4
.FirstPageNumber = xlAutomatic
.Order = xlDownThenOver
End With
.ResetAllPageBreaks
.HPageBreaks.Add .Range("I100")
For i = 1 To 29
.VPageBreaks.Add .Cells(1, i * 8)
Next
.PrintOut Copies:=1
End With
Application.Goto Sheets("Header").Range("A1")
End sub